GB2286024A

GB2286024A - Preventing disengagement of seal member in a booster

Info

Publication number: GB2286024A
Application number: GB9426336A
Authority: GB
Inventors: Makoto Watanabe
Original assignee: Jidosha Kiki Co Ltd
Current assignee: Jidosha Kiki Co Ltd
Priority date: 1994-01-28
Filing date: 1994-12-29
Publication date: 1995-08-02
Anticipated expiration: 2014-12-29
Also published as: GB2286024B; JP2894423B2; US5586481A; KR950023564A; JPH07215205A; GB9426336D0; CN1115729A; KR970009633B1; CN1076449C

Abstract

A booster e.g. for a brake of an automobile comprises a bearing (36) which supports a valve body (6a) for sliding movement relative to a stepped tubular portion (2A) of a rear shell (2), and an annular seal member (10) for effecting a seal between the valve body and the stepped portion. A circumferential rib or a plurality of circumferentially spaced projections (10c; 36a) are formed at the outer periphery of either of the opposed end faces of the seal member (10) and the bearing (36) to prevent the seal member from being disengaged from the step of the stepped tubular portion in the rearward direction when the seal member and the bearing are sequentially fitted inside the stepped tubular portion from the front. <IMAGE>

Description

1 2286024 Apparatus for preventing disengagement of seal member in a

booster The invention relates to a booster as used in a brake of an automobile, and more particularly, an apparatus for preventing disengagement of a seal member interposed between a tubular terminal end of a valve body and a stepped tubular portion of a shell.

As is known in the art, a booster comprises a shell including a stepped tubular portion extending axially rearward from a rear end of the shell and having a step formed therein, the tubular portion having a greater diameter forwardly of the step, a valve body disposed within the shell in a reciprocable manner and including a tubular terminal end which projects axially rearwardly through the stepped tubular portion of the shell, a bearing disposed within a portion of the shell having a greater diameter for slidably supporting the tubular terminal end of the valve body, and an annular seal member disposed within the portion 2 - of the shell having a greater diameter and is held sandwiched between the step and the bearing for sealing between the stepped tubular portion and the tubular terminal end of the valve body.

The seal member includes an annular portion of an increased wall thickness which is fitted inside the shell portion having a greater diameter, and an annular lip portion extending rearward and radially inward in an oblique manner from the front side of the annular portion, and is generally V-shaped in crbss section. The front end face of the seal member, or the end face which faces the bearing, is formed in a plane which is substantially orthogonal to the axial direction.

During the assembly of the seal member, the seal member is initially fitted inside a portion of the stepped tubular-portion which has a greater diameter, followed by fitting the bearing into the same portion, whereupon the bearing is pushed through a given stroke into the tubular portion having a greater diameter so that the-seal member is held sandwiched between the bearing and the step of the stepped tubular portion. Under this condition, the outer annular portion having an increased wall thickness is held sandwiched between the step and the bearing to provide a seal between 01 the outer peripheral surface of the annular portion and the inner peripheral surface of the stepped tubular portion. The lip portion is disposed in sliding contact with the outer peripheral surface of the tubular terminal end of the valve body to seal it.

It will be seen that duxing the assembly of the seal member mentioned above, the end face of the seal member which faces the bearing is urged into contact with the bearing and that due to manufacturing tolerances, the front end face of the seal member may be driven into contact with the bearing around its inner periphery. In this event, the inner periphery of the seal member which contacts the bearing, and which is located radially inward of the end face of the annular portion of the seal member which contacts the step of the stepped tubular portion by an amount corresponding to the thickness of the lip portion, may be forcibly pushed inside the annular seal member, in a manner as if folded back upon itself, accompanying deformation while being rotated around the step of the stepped tubular portion as the seal member is pushed inward, thereby causing a disengagement of the seal member from the step or producing a likelihood that the sealing capability may be degraded.

In view of the foregoing, the present invention provides an apparatus for preventing disengagement of a seal member in a booster which positively prevents an inner periphery of the seal member from becoming contacting the bearing during the assembly of the seal member, thereby avoiding any reduction in the sealing capability and the likelihood of the seal member being disengaged rearwardly from the step.

Specifically, the invention can provide improvement in a booster which is constructed in a known manner as mentioned above, the improvement comprising the provision of a projection provided on one of an outer periphery of the end face of the seal member which faces the bearing or an outer periphery of the end face of the bearing which faces the seal member and projecting toward the other.

With this arrangement, the seal member and the bearing will contact with each other through the projection provided on the outer periphery of either member during the assembly of the seal member, whereby the seal member will be held sandwiched between the projection on the outer periphery and the step of the stepped tubular portion which is disposed in surrounding relationship therewith. Consequently, the inner periphery of the seal member is no longer subject to any action which would forcibly drive such portion inside the annular seal member while causing a deformation thereof. Accordingly, a disengagement of the seal member is prevented, assuring a reliable sealing function.

-Above and other objects, features and advantages of the invention will become apparent from the following description of several embodiments thereof with reference to the attached drawings. In the drawings: -

Fig. 1 is of the invention; Fig. 2 is a cross section, to an enlarged scale, of a seal member 10 which is assembled; Fig. 3 is an enlarged cross section illustrating an operation which assembles the seal member 10; Fig. 4 is a cross section of part of another embodiment of the invention; and Fig. 5 is a cross section of a further embodiment of the invention.

a longitudinal section of one embodiment Referring to Fig. 1, a front and a rear shell 1, 2 define together an enclosed vessel, and a center plate 3 which is centrally disposed therein divides the interior of the vessel into a p - air of front chamber 4 and rear =hamber 5. A substantially t ubular valve body 6 slidably extends through an axial portion of the center plate 3 and is hermetically sealed thereagainst by an annular seal member 7. A tubular terminal end 6a of the valve body 6 projects axially rearward of a stepped tubular portion 2A which in turn extends radially rearward from a rear end face of the rear shell 2. A seal member 10 is provided between the tubular terminal end 6a and the stepped tubular portion 2A to provide a seal therebetween.

A front power piston 11 and a rear power piston 12, which are disposed within the front and the rear chamber 4, 5, respectively, are connected to the valve body 6, and a front and a rear diaphragm 13, 14 are applied to the back surfaces of the power pistons 11, 12, respectively, thus defining a constant pressure chamber A and a variable pressure chamber B across the front diaphragm 13 and defining a constant pressure chamber C and a variable pressure chamber D across the rear diaphragm 14.

The valve body 6 contains a valve mechanism 15, which comprises an annular, first valve seat 16 formed on the valve body 6, an annular, second valve seat 18 7 R - 7 formed on the right end of a valve plunger 17, which is reciprocably mounted on the valve body 6 at a location Tad.jIally inward of the first valve seat 16, and a valve element 20 which is urged by a spring 19 from right to left, as viewed in Fig. 1, so as to be s.eated upon either valve seat 16 or 18.

A space which is located radially outward of an annular seat defined by a contact between the first valve seat 16 and the valve element 20 communicates with the constant pressure chamber A through an axial constant pressure passage 22A which is formed in the valve body 6, and the chamber A in turn communicates with an intake manifold of an engine, not shown, through a tubing 23 which serves introducing a negative pressure. The -constant pressure chamber A is maintained in communication with the constant pressure chamber C through another axial constant pressure passage 22B, also formed in the valve body 6.

On the other hand, a space located radially inward of the annular scat defined by the contact between the first valve seat 16 and the valve element 20, but radially outward of an annular seat defined by the contact between the second valve seat 18 and the valve element 20, or located intermediate the inner and the outer annular seats, communicates with 8 the variable pressure chamber D through a radial variable pressure passage 24 formed in the valve body 6, and the chamber D in turn communicates with the variable pressure chamber B through another variable pressure passage 25 also formed in the valve body 6.

Finally, a space located radially inward of the inner annular seat defined by the contact between the second valve seat 18 and the valve element 20 communicates with a pressure passage 26 which in turn communicates with the atmosphere.

The valve plunger 17, which is slidably disposed within the valve body 6, has its right end connected to an input shaft 28 which is mechanically coupled to brake pedal, not shown, and a plunger plate 29 and reaction disc30 are sequentially disposed to the left of the valve plunger 17. The reaction disc 30 is received in a recess which is formed in the right end of a push rod 31, the left end of which slidably extends through a seal member 32 to project through the axial portion of the front shell 1 for connection with the piston of a master cylinder, not shown. The valve body 6 is normally maintained in its inoperative position shown by a return spring 33.

As shown to an enlarged scale in Fig. 2, the. stepped tubular portion 2A which is formed to extend 7 -9 A 1.

9 - from the rear axial portion of the rear shell 2 includes a portion of a greater diameter 2a which is located foremost, a step 2b which is bent radially inward from the rear end of the portion 2a, and a portion 2c of a reduced diameter which extends rearwardly from the step 2b. A dust cover 35 (see Fig. 1) has its left end mounted around the periphery of the portion 2c.

The seal member 10 which provides a seal between the tubular terminal end 6a of the valve body 6 and the stepped tubular portion 2A comprises an annular portion 10a of an increased thickness which is fitted inside the portion 2a of a greater diameter, and an annular lip.portion 10b which extends from the front side of the annular portion 10a rearwardly and radially inward in an oblique manner so as to present a cross section which is substantially V-shaped. In the embodiment shown, the front end face of the seal member is bevelled so as to present a plane which is at an angle with respect to the axial direction so that the inner periphery thereof projects forwardly of the outer periphery. In addition, a plurality of projections 10c (see Fig. 3) are formed on the front end face of the seal member around its outer periphery at an equal spacing as viewed in the circumferential direction, and project forwardly.

A bearing 36 is disposed forwardly of the seal member 10 around the portion 2a having a greater diameter of the stepped tubular portion 2A so as to support the tubular terminal end 6a of the valve body 6 in a reciprocable manner. The bearing 36 is normally urged to a position which is located a given distance L from the inner wall surface of the rear shell 2 as a reference, and is held in place by a retainer 37.

During the assembly of the seal member 10 in the described arrangement, the seal member 10 is initially fitted around the portion 2a having a greater diameter of the stepped tubular portion 2A, as shown in Fig. 3, and the bearing 36 and the retainer 37 are sequentially fitted inside the portion 2a. By employing a jig, not shown, the bearing 36 and the seal member 10 are urged toward the step 2b through the retainer 37 until the bearing 36 is displaced to the given distance L as referenced to the inner wall surface of the rear shell 2, whereupon the bearing 36 is maintained in place.

During such process, the projections 10c which are formed on the seal member 10 around its outer periphery abut against the bearing 36, whereby the seal member 10 is held sandwiched between such projections 10c and the step 2b of the stepped tubular portion 2A, thus preventing the inner peripheral portion of the seal OS 1 xl 11 - member from being driven radially inward while it is being deformed.

To consider this, assume that the projections 10c are not provided. In this instance, an inner peripheral portion 10d of the seal member 10 will abut against the bearing 36. Since the inner peripheral portion 10d which abuts against the bearing 36 is located radially inward of the right end face of the annular portion 10a which is disposed in contact with the step 2b of the stepped tubular portion 2A, by an amount corresponding to the thickness of the lip portion 10b, there is a likelihood that as the seal member 10 is urged, the inner peripheral portion 10d thereof will be rotated about the step 2b to be deformed inside the annular seal member 10, thereby causing the seal member 10 to be disengaged from the step lb in the rear direction or degrading the sealing capability if such disengagement does not occur.

However, according to the present embodiment, such disengagement can be prevented., and the seal member 10 may be reliably positioned in place where the annular portion 10a of the seal member 10 is held sandwiched between the step 2b of the stepped tubular portion 2A and the bearing 36 to provide a seal between the outer peripheral surface of the annular portion 10a and the inner peripheral surface of the stepped tubular 12 portion 2A. When the valve body 6 is assembled therein subsequently, the annular lip portion 10b of the seal member 10 will be in sliding contact with the outer peripheral surface of the tubular terminal end 6a of the valve body 6, thus providing a sealing action.

Fig. 4 shows another embodiment of the invention in which a plurality of projections 36a are formed on the bearing 36 around its outer periphery at an equal circumferential spacing so as to project toward the seal member 10, and act in the similar manner as the projections 10c formed on the seal member 10 in the previous embodiment. In other respects, the arrangement is similar to the previous embodiment, and corresponding parts are designated by like numerals and characters. It will be evident that this embodiment achieves the similar functioning and effect as achieved by the first embodiment.

In the described embodiments, the projections 10c on the seal member 10 or the projections 36a on the bearing 36 are plural in number and are circumferentially spaced apart, and accordingly balancing the loading against the hermetic sealability is facilitated by choosing a suitable size or suitable number for such projections. However, it should be understood-that rather than providing a plurality of projections 10c v J or 36a, a single projection which is continuous in the circumferential direction may be used, and this again is effective to prevent the disengagement of the seal member 10 (see Fig. 5). (An annular projection 36a which is circumferentially continuous is not specifically shown-since the illustration is similar to Fig. 4).

While the invention has been disclosed above in connection with the several embodiments thereof, it should be understood that a number of changes, modifications and substitutions therein are possible from the above disclosure without departing from the spirit and scope of the invention defined by the appended claims.

I-

Claims

WHAT IS CLAIMED IS:

1. In a booster comprising a shell including a stepped tubular portion which extends axially rearward from a rear end face of the shell and having a step formed therein, the stepped tubular portion having a greater diameter forwardly of the step, a valve body disposed within the shell so as to be reciprocable and including a tubular terminal end which projects axially rearward through the stepped tubular portion, a bearing disposed within a portion of the stepped tubular portion which has a greater diameter for slidably supporting the tubular terminal end of the valve body, and an annular seal member disposed within the portion of the stepped tubular portion having a greater diameter so as to be held sandwiched between the step and the bearing to provide a seal between the stepped tubular portion and the tubular terminal end of the valve body; an apparatus for preventing a seal member in a booster characterized by a projection formed on one of an end face of the seal member which faces the bearing around its outer periphery or an end face of the bearing which faces the seal member around its outer periphery and projecting toward the other.

C is

2. An apparatus according to Claim 1 in which the bearing is fitted inside the portion of the stepped tubular portion having a greater diameter from the front side thereof and is positioned at a given axial position therein by a retainer which is disposed in abutment against the bearing, and in which the seal member comprises an annular portion having an increased wall thickness which is fitted within the portion of the stepped tubular portion having a greater diameter and is disposed in contact with the step, and a lip portion located radially inward of the annular portion and disposed for sliding contact with the outer peripheral surface of the tubular terminal end of the valve body.

3. An apparatus according to Claim 2 in which an end face of the seal member which faces the bearing is tapered so that the inner periphery thereof projects forwardly of the outer periphery, the projection being formed on the end face of the seal member which faces the bearing at a plurality of locations which are circumferentially spaced apart around the outer periphery thereof.

16 -

4. An apparatus according to Claim 2 in which the end face of the seal member which faces the bearing is tapered so that the inner periphery thereof projects forwardly of the outer periphery, and in which the projection comprises an annular projection formed on the end face of the seal member which faces the bearing around the outer periphery and which is circumferentially continuous.

5. An apparatus according to Claim 2 in which the projection is formed on the end face of the bearing which faces the seal member around its outer periphery at a plurality of locations and which are circumferentially spaced apart.

6. An apparatus according to Claim 2 in which the the projection comprises an annular projection which is formed on the end face of the bearing which faces the seal member around its outer periphery and which is circumferentially continuous.

R 17

7. A booster comprising a shell having a tubular portion extending axially rearward extension from an end face of the shell, said portion being formed with a step and having a greater diameter region forward of the step, a valve body reciprocable within the shell having an end which projects axially through the stepped tubular portion, a bearing disposed within the greater diameter region of the stepped tubular portion for slidably supporting said end of the valve body, and an annular seal member disposed within said greater diameter region so as to be held between the step and the bearing and providing a seal between the stepped tubular portion and the end of the valve body projecting therethrough, the bearing and the seal member having opposed end faces on one of which at least one retaining projection is formed projecting toward the other end face.

8. A booster constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.